FACTORS AFFECTING THE FRACTURE TOUGHNESS OF HIGH STRENGTH STEEL WELDMENTS

Over the past decade considerable research and development efforts have been directed towards assessment of weld metal and heat-affected zone microstructures and their resultant mechanical properties. In this presentation an overview of several R&D investigations conducted at CANMET will be described. In studying the factors that affect the fracture behaviour of high strength steel weldments a primary goal has been optimizing welding consumables and procedures, as well as developing appropriate testing techniques for evaluation of weld metal and heat-affected zone regions of multipass weldments. The influence of energy input, proportion of as-deposited to reheated, and the final weld metal microstructure and hardness are important factors to be considered in explaining the variations in weld metal toughness for welds produced in both HY and HSLA steels. For HAZ evaluations, the influences of base metal chemistry, welding thermal cycle, and effects of local brittle zone and strength mismatch are important in understanding and controlling the fracture toughness of the HAZ region.